JP3525626B2 - Pigment composition for liquid toner - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a pigment composition for liquid toner.

[0002]

2. Description of the Related Art According to a wet electrophotographic printing method, a printing speed is inferior to that of a commercial offset rotary press but is much larger than that of a general dry copier, and unlike a commercial offset rotary press, a plate is not replaced. Higher image quality (resolution of 800 DPI or more) that is comparable to photos at a reduced printing unit price
It is possible to obtain a printed matter. A so-called liquid toner is used for this type of development, and the toner is composed of an electrically insulating liquid and pigment fine particles dispersed therein. Here, a resin is used by being dissolved in the electrically insulating liquid for the purpose of dispersing and fixing pigment fine particles.

[0003]

In this liquid toner, when carbon black containing a large amount of grit and ash is used, not only the photoreceptor is damaged but also a printed matter having a halftone dot shape is disturbed, so that the amount of these substances is small. One of the important issues is how to make toner using carefully selected carbon black.

[0004]

Therefore, the present inventor has made various studies in order to obtain a pigment composition for a liquid toner, which has solved the above-mentioned problems, and arrived at the present invention. That is, the gist of the present invention is to dissolve carbon black and resin in a non-aqueous solvent.
A pigment composition for liquid toner, wherein the carbon black has a grit content of 10 ppm or less and an ash content of 0.5 wt% or less.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.
First, in the pigment composition for a toner of the present invention, as the carbon black, it is necessary to use carbon black having a grit content of 10 ppm or less among carbon black produced by a furnace method, a contact method, an acetylene method or the like. .

[0006] Generally, carbon black is a foreign substance having a size of 44 μm or more (so-called grit, which is a main component of coke grains and brick exfoliation generated in the manufacturing furnace at the same time as the production of carbon black, and metals generated from a heat exchanger or the like. The carbon black currently available in the market is mixed in a small amount of 50 ppm or more.

When the grit is mixed in an amount of 10 ppm or more, the surface of the photoconductor or the transfer roll, which can be said to be the heart of the wet electrophotographic printing machine, is not only scratched but causes scumming, and the dot shape of printing is disturbed. Absent. Carbon black having a grit of 10 ppm or less, preferably 5 ppm or less, has an average particle size of 10 to 100 nm, DBP
(Dibutyl phthalate) Oil absorption 40-300 ml / 10
0 g, specific surface area 20 to 1000 m ² / g, pH ^{2 to} 10
After uniformly suspending carbon black having the characteristics described above in water to obtain a liquid having a viscosity of 1 to 100 poise, a wet vibration sieve is disclosed.
No. 6-11963) or an ultrasonic classifier (Japanese Patent Laid-Open No. 61-89262) to remove impurities of 44 μm or more.

Particularly preferred is an average particle size of 20-50.
nm, DBP oil absorption 50 to 150 ml / 100 g, specific surface area 50 to 150 m ² / g, carbon black having a pH of 2.0 to 6.0 is treated with the aforementioned wet classifier or ultrasonic classifier, and the grit is preferably 10 ppm or less. Is carbon black of 5 ppm or less. The grit is JIS-
K-6221-1970 Sieve Residue Measured based on the A method.

Carbon black was put into a 350 mesh sieve little by little, water was poured from the nozzle into the sieve, the carbon black was washed off until the water passing through the sieve became transparent, and the residue remaining on the sieve was kept at 105 ° C. for 1 hour. After drying and cooling, the weight thereof is measured and the sieve residue (grit) is calculated by the following formula.

The grit measurement is carried out using a carbon black amount of 500 to 1000 g. Next, as the carbon black used in the toner pigment composition of the present invention, it is necessary to use a product having an ash content of 0.1% by weight or less in accordance with a grit content of 10 ppm or less.

The composition of the ash is formed by alkali metals, alkaline earth metals, and salts and oxides thereof, and when carbon black is contained in an amount of more than 0.1% by weight, the conductivity of the liquid toner is increased. The electrostatic static image on the surface of the photoconductor is disturbed, and as a result, a high-density image cannot be obtained. In addition, the alkaline ion substance in the ash is adsorbed on the toner particles and interferes with the adsorption of the charge control agent, so that the zeta potential is lowered and the edges of the image area and the non-image area are destroyed, and not only the resolution is deteriorated. It is not preferable because it becomes a so-called "nebulized image".

In order to reduce the ash content, it is possible to examine the raw material oil at the time of producing carbon black, the spray water used at the time of quenching, and the additives.
It can also be achieved by washing the carbon black produced from the production furnace with water or pickling. Further, it can be achieved by combining the examination of raw materials, spray water, additives and the like at the time of production with washing with water, pickling and the like. The content of ash present in carbon black is represented by the amount that remains when the carbon black is calcined in air at 750 ° C. for 4 to 6 hours.

The resin of the present invention is preferably a thermoplastic resin. For example, vinyl chloride resin, vinylidene chloride resin, vinyl acetate resin, polyvinyl acetal resin, styrene resin, methacrylic acid resin, polyethylene resin, polypropylene resin, fluorine resin, polyamide resin, polyacetal resin, saturated polyester resin, etc. Is particularly preferably an olefin resin having a carboxyl group or an ester group, such as ethylene.
Vinyl acetate copolymer, partially saponified ethylene / vinyl acetate copolymer, ethylene / (meth) acrylic acid copolymer, ethylene / (meth) acrylic acid ester copolymer,
(Meth) acrylic ester resin, styrene / (meth)
Examples thereof include acrylic acid copolymers and styrene / (meth) acrylic acid ester copolymers. It is also possible to use one kind or a mixture of two or more kinds from these.

Furthermore, a charge control agent and / or a dispersant may be added to the pigment composition for liquid toner of the present invention. As the charge control agent, those conventionally used for charge control of developers, for example, nigrosine dye, manganese naphthenate, calcium naphthenate, zirconium naphthenate,
Cobalt naphthenate, iron naphthenate, lead naphthenate, nickel naphthenate, chromium naphthenate, zinc naphthenate, magnesium naphthenate, manganese octylate, calcium octylate, zirconium octylate, iron octylate, lead octylate, octylate Cobalt, chromium octylate, zinc octylate, magnesium octylate,
Metallic soaps such as manganese dodecylate, calcium dodecylate, zirconium dodecylate, iron dodecylate, lead dodecylate, cobalt dodecylate, nickel dodecylate, chromium dodecylate, zinc dodecylate, magnesium dodecylate, calcium dodecylbenzenesulfonate, Alkylbenzenesulfonates such as sodium dodecylbenzenesulfonate and barium dodecylbenzenesulfonate,
Examples thereof include phospholipids such as lecithin and sehalin, and organic amines such as n-decylamine. These can be used alone or in combination of two or more kinds. The addition amount of the charge control agent may be the minimum amount showing the charge control effect, but it is usually 0.5 to 50% by weight, preferably 1 to 30% by weight in the solid content of the liquid toner.

Next, as the dispersant used in the present invention, a surfactant to which ethylene oxide is added as a hydrophilic group is suitable. Specific examples include phosphoric acid ester salts of higher alcohol ethylene oxide adducts, which are classified as phosphoric acid ester salts among anionic surfactants,
The nonionic surfactants include higher alcohol ethylene oxide adducts, alkylphenol ethylene oxide adducts, fatty acid ethylene oxide adducts, polyhydric alcohol fatty acid ester ethylene oxide adducts,
Examples include higher alkylamine ethylene oxide adducts, fatty acid amide ethylene oxide adducts, ethylene oxide adducts of fats and oils, polypropylene glycol ethylene oxide adducts, and the like, and they can be used alone or in combination of two or more kinds. The amount of these dispersants added is usually
The content of the solid content of the liquid toner is 0.5 to 80% by weight, preferably 1 to 50% by weight.

In the present invention, for example, the above carbon black and resin are first kneaded. When kneading,
The resin is preferably crushed in advance to remove coarse particles. A resin and carbon black, preferably, a charge control agent and / or a dispersant are blended, and a Henschel mixer, a cooler mixer, a Nauta mixer, a drum mixer,
After mixing using a tumbler or the like, the mixture is kneaded by a Banbury mixer, a co-kneader, a two-roll mill, a three-roll mill, a single-screw extruder, a twin-screw extruder or the like. The compounding ratio of the resin and carbon black is 50 to 99.9% by weight of the resin,
Pigments of 50 to 0.1% by weight are preferred.

The kneaded material obtained is then preferably freeze-ground. For example, after sufficiently cooling with dry ice or liquid nitrogen, or under an atmosphere in which these refrigerants are made to flow, a jet mill, a jet-o-mizer, a counter jet mill, or a super hammer mill is used.
It is frozen and pulverized to 0 μ or less, preferably 500 μ or less.
Further, after the pulverization, it is possible to further improve the dissolution / dispersion efficiency in the next step by classifying the particles into a desired particle size with a classifier such as a micron separator, a turbo classifier, a micron classifier and removing coarse particles, which is preferable.

Next, it is dissolved / dispersed in a non-aqueous solvent. Examples of the non-aqueous solvent include linear or branched chain aliphatic hydrocarbons, halogenated aliphatic hydrocarbons, aromatic hydrocarbons, aliphatic alcohols, ethers and the like. Specifically, as the non-aqueous solvent that does not dissolve the resin, "Isoper G", "Isoper H", "Isoper K", "Isoper L", "Isoper M", manufactured by Exxon Co.,
"Isopar V", Shell Oil Company's "Shellsol 7"
1 "," IP1620 "," IP2 "manufactured by Idemitsu Petrochemical Co., Ltd.
"028", "IP2835" and the like are preferable. Further, as the non-aqueous solvent that dissolves the resin, benzene, toluene,
Methyl ethyl ketone, acetic acid ester, ethyl ether,
Tetrahydrofuran and the like are preferable, and these are alone or
Two or more kinds can be used in combination. Regarding the compounding ratio of the solvent and the above kneaded / pulverized product at the time of dispersion, it is preferable to disperse the solvent by adding 3 to 8 times by weight, preferably 4 to 7 times by weight of the kneaded product.

In the dispersion, for example, in order to dissolve the resin and reduce the viscosity, the finely pulverized kneaded product is put in a solvent heated to 60 to 80 ° C. and stirred lightly to completely dissolve it. It is preferably carried out. As the disperser, a ball mill, a pebble mill, an attritor, a sand grinder (vertical type, a horizontal type) or the like can be used, and among them, a sand grinder commercially available under the trade names of “Dyno mill” and “Cobra mill” is preferable.

The temperature of the solution at the time of dispersion varies depending on the type of resin and solvent, but is usually preferably about 60 to 80 ° C. On the other hand, the dispersion time is preferably tracked by a grind gauge, a microscope or the like for each dispersion time, and the dispersion is preferably performed until there are substantially no aggregates of 5 μm or more, preferably 3 μm or more. Then, a non-aqueous solvent that does not dissolve the resin is added to the obtained dispersion liquid to obtain a desired carbon black concentration, and then carbon black and resin particles are deposited by a conventional method to obtain the intended liquid toner.

[0021]

The present invention will be described in more detail based on the following examples. Parts in the examples represent parts by weight, and% represents% by weight. [Example 1] Carbon black was produced by an ordinary oil furnace method. However, as the raw material oil, Na, C
Ethylene bottom oil with a small amount of a and S was used, and coke oven gas was used for combustion. Further, as the reaction stopped water, pure water treated with an ion exchange resin was used for production.

The resulting carbon black was added to pure water to prepare a suspension type T.P. A uniform suspension containing 1-2% by weight of carbon black was prepared by vigorously stirring with a K homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.). 50cm diameter after confirming viscosity
Treated with a vibrating screen equipped with a 500 mesh wire mesh, and then added a predetermined amount of toluene to the filtered suspension and stirring,
The carbon black was transferred to the toluene phase and simultaneously granulated.

The carbon black obtained was separated from water by sieving and separated, and heated to 100 to 200 ° C. to remove toluene and water, and then the grit, ash, DBP oil absorption, specific surface area and the like were measured. The results are shown in Table 1. Next, capacity 20
Liter super mixer (Kawata SMV-2
Type 0)) partially saponified ethylene / vinyl acetate copolymer "Dumilan C-2280" (manufactured by Takeda Pharmaceutical Co., Ltd.) 2400
g and 600 g of the above carbon black, and further nigrosine ("Bontron N-09" manufactured by Orient Chemical Co., Ltd.) 30
g, "MRB-8" (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.), and mixed at 2000 rpm for 5 minutes. Next, this mixture was kneaded by a twin-screw extruder (“TEM-35B” manufactured by Toshiba Machine Co., Ltd.) set to a maximum temperature of 150 ° C., and then cut into a diameter of about 1 to 2 mm by a strand cutter to obtain kneaded pellets.

Next, the pellets were immersed in liquid nitrogen and sufficiently cooled, and then jet mill (“STJ-20” manufactured by Seishin Enterprise Co., Ltd.) was used.
0 "). The crushed product was dried for 10 hours by a vacuum dryer set at 70 ° C. The average particle size of the ground product was 120 μm. Then, "Isopar G"
(Esso Oil Co., Ltd.) 48%, Toluene (Katayama Chemical Co., Ltd.)
2550 g of a mixed solution of 32% and 20% ethanol (manufactured by Katayama Chemical Co., Ltd.) and 450 g of the crushed product were placed in a stainless steel container, gradually heated while stirring at 100 rpm, and kept at 70 ° C. for 30 minutes. Dissolved.

Then, the melt was kneaded into a "Dyno-mill" (KDL-Pilot type, sold by Shinmaru Enterprises Co., Ltd.) having a volume of 1.4 liters and a solution at 70 ° C. was used for 3.5 times.
It was introduced at a rate of liter / min and dispersed for 3 hours.
A part of the dispersion liquid is thinly applied to a glass plate and the optical microscope 400 is used.
As a result of observing the dispersibility by a factor of two, there were no aggregates of 1 μm or more.

Next, in a container equipped with a stirrer, a thermometer, and a reflux condenser, 2.0 parts of the above dispersion liquid and 150 of the above mixed solvent were placed.
Part, "MRD-8" 0.24 part, "Dumilan C-22
80 "0.4 part was added and stirred at 70 ° C for 30 minutes to completely dissolve" Dumilan C-2280 ", and then 30 minutes at room temperature.
It was left to cool to 0 ° C. to precipitate pigment resin particles. The mixed solvent of this pigment resin particle dispersion is replaced with "ISOPER G",
Zirconium naphthenate was added as a charge control agent to obtain a positively charged liquid toner.

Table 1 shows the evaluation results of the physical properties and image quality of the liquid toner. The toner particle size is LA-700, a laser diffraction / scattering particle size distribution meter manufactured by Horiba, Ltd., and the zeta potential is a laser zeta electrometer “LEZA-6” manufactured by Otsuka Electronics Co., Ltd.
00 ”was used for the measurement. The image quality was evaluated by visual inspection by printing on coated paper using "Mitsubishi Electronic Printing System". The image density was measured using a Macbeth densitometer.

[Example 2] and [Comparative Examples 2 and 3] All were carried out in the same manner as in Example 1 except that the carbon black of Example 1 was changed to the grade shown in Table 1. The evaluation results of physical properties and image quality are as shown in Table 2.

[0029]

[Table 1]

[0030]

[Table 2]

[0031]

According to the present invention, it is possible to obtain a pigment composition for liquid toner which can obtain good image characteristics.

─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Yasuharu Suda 4-6-22 Kannon Shinmachi, Nishi-ku, Hiroshima Sanryo Heavy Industries Co., Ltd. Hiroshima Research Institute (72) Inventor Katsuaki Makino 4-22 Kannon Shinmachi, Nishi-ku, Hiroshima Sanritsu Heavy Industry Co., Ltd. Hiroshima Laboratory (56) References JP-A-8-176463 (JP, A) JP-A-9-194755 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB) Name) G03G 9/12 311 G03G 9/08 C09C 1/48

Claims (3)

(57) [Claims] 1. A pigment composition for a liquid toner, comprising carbon black and a resin dissolved and dispersed in a non-aqueous solvent, wherein the carbon black has a grit content of 10 ppm or less and an ash content of 0.1 wt% or less. object. 2. The pigment composition for a liquid toner according to claim 1, which has a grit content of 5 ppm or less. 3. An average particle diameter of 2 as carbon black.
0 to 50 nm, DBP oil absorption 50 to 150 ml / 100
g, specific surface area 50 to 150 m ² / g, pH 2.0 to 6.
The pigment composition for liquid toner according to claim 1 or 2, which is obtained by treating the carbon black of No. 0 with a wet classifier or an ultrasonic classifier.